Open crystals are sparsely populated periodic structures, which, when composed of colloidal particles, are appealing for their variety of applications, for example, as photonic materials, phononic and mechanical metamaterials, as well as porous media [1-4]. Programming self-assembly of colloidal particles into open crystals has proved a long-standing challenge due both to the mechanical instability and lack of kinetic accessibility that colloidal open crystals typically suffer from. Building on our recent work [5-7], I will here introduce a hierarchical self-assembly scheme for triblock patchy particles to address the challenges met with programming self-assembly into colloidal open crystals [8]. The presentation will demonstrate in silico the hierarchical self-assembly of colloidal open crystals via what we call closed clusters, which stop to grow beyond a certain size in the first stage and are thus self-limiting [8]. Our designer patchy particles are spherical in shape, having two attractive patches at the poles across a charged middle band – a close variant of those synthesised recently [9]. By employing a variety of computer simulation techniques, I will show that the design space supports different closed clusters (e.g. tetrahedra or octahedra with variable valences) en route to distinct open crystals. Our design rules thus open up the prospects of realising a number of colloidal open crystals from designer triblock patchy particles, including, most remarkably, a diamond crystal [8], much sough-after for is attractive photonic applications. The relevant photonic band structure will be presented.